The present disclosure relates to extracorporeal blood circuit devices and related methods of use. More particularly, it relates to oxygenator devices (or combination devices including an oxygenator) for oxygenating blood in an extracorporeal blood circuit with improved outlet blood sampling accuracy.
An extracorporeal blood circuit is commonly used during cardiopulmonary bypass to withdraw blood from the venous portion of the patient's circulation system (via a venous cannula) and return the blood to the arterial portion (via an arterial cannula). The extracorporeal blood circuit typically includes a venous drainage line, a venous blood reservoir, a blood pump, an oxygenator, a heat exchanger, one or more filters, and blood transporting tubing, ports, and connection pieces interconnecting the components. Oftentimes, two or more components can be combined into a single device, such as a combination oxygenator and heat exchanger.
Blood oxygenators are disposable components of extracorporeal circuits and are used to oxygenate blood. In general terms, the oxygenator takes over, either partially or completely, the normal gas exchange function of the patient's lungs. The oxygenator conventionally employs a microporous membrane or bundle comprised of thousands of microporous or semipermeable hollow fibers. Blood flow is directed around the outside surfaces of hollow fibers. Concurrently, an oxygen-rich gas mixture is passed through the fiber lumens. Due to the relatively high concentration of carbon dioxide in the blood arriving from the patient, carbon dioxide is transferred from the blood, diffusing across the microporous fibers and into the passing stream of oxygenating gas. At the same time, oxygen is transferred from the oxygenating gas, diffusing across the fibers and into the blood. The oxygen content of the blood is thereby raised, and the carbon dioxide content is reduced.
After the blood has flowed around the fibers of the oxygenator bundle it must be routed outside the oxygenator housing via a blood outlet port. The perfusionist often desires to monitor various parameters of the blood as it exits the oxygenator. To meet this need, many available oxygenators incorporate one or more sampling or auxiliary ports at the blood outlet port and through which samples can be taken and/or other information obtained. For example, blood oxygenators can incorporate a sampling port for obtaining samples of the oxygenated blood (e.g., for blood gas analysis) and/or a monitoring port through which a temperature monitoring probe (or other device) can interface with the blood.
Because the sampling ports are provided along the blood outlet port, the blood flow path immediately upstream of the blood outlet port is of interest. Many currently available blood oxygenators (including oxygenators with an integrated heat exchanger) incorporate a generally cylindrically-shaped outer housing or case, with the blood outlet port being located at a side of the case. With this construction, blood flow through the oxygenator membrane is directed along the outer housing (and elsewhere within the case) to a single opening into the blood outlet port. This single opening port design is essentially an industry standard, and is conventionally understood as contributing to a low as possible prime volume attribute of the oxygenator. While well-accepted, the single opening blood outlet port design may limit the accuracy of blood-related parameters sensed or sampled at the blood outlet port.
In light of the above, a need exists for improved oxygenator designs that improve the accuracy of sensed or sampled blood-related parameters at the blood outlet port.